Off road vehicles (ORVs) as defined for the purposes of this invention consist of off-road motorcycles, three and four wheel all terrain vehicles (ATVs), dune buggies, two and four wheel drive off-road trucks, amphibious vehicles (water to land, and back) and hovercraft. The invention could be adapted for use on any of these ORVs, however, for the purposes of discussion will be described as sued on the racing type of off-road motorcycle called motocross bikes. The exhaust system on a motocross bike's internal combustion engine typically consists of an exhaust pipe and a silencer which are designed as a customized system to insure maximum power output from each different model engine. Although the silencers provided by the original equipment manufacturer reduce engine noise output to a degree, this reduced sound level remains unacceptably high for use near residential areas. Many motocross bikes, which were originally designed for race use on private courses, are used for non-competitive "trail riding" on public and private lands that are near residential areas. For use on public lands. The Department of Natural Resourses (DNR) requires that ORVs not exceed specified noise levels. For example, in the case of motorcycles manufactured after Jan. 1, 1986 the maximum noise level is 94 decibels (dba) when measured per test procedure SAE J 1287. Typically a motocross bike with a standard silencer will yield over 100 dba under this same test. Additionally, the DNR requires that all off-road vehicles be equipped with a U.S. Forest service approved spark arrester that captures at least 80 percent of carbon particulate carried by the exhaust gases to minimize the risk of exhaust spark fires.
Original equipment manufactures such as Honda and Kawaski have never been required to produce motocross bikes pre-equiped to meet the DNRs spark arrester and noise requirements because their designed use is for racing on private lands, Thus, aftermarket manufactures have been left to produce spark arrester and silencer products to meet the DNR regulations.
However, the two greatest obstacles to designing an aftermarket silencer and/or spark arrester product are first fitting the product onto the multitude of uniquely shaped exhaust systems for each motorcycle brand, model size and model year and second, maintaining adequately sized exhaust flow corridors through the product so it will not hinder performance characteristics of each uniquely designed exhaust system. Over the last two decades there have been over fifteen different brands of motocross bikes sold in the United States and each brand has typically offered two to four different model sizes. With the exhaust system configuration of each model size changing from year to year, hundreds of different exhaust systems have resulted.
As a consequence, aftermarket manufacturers have only been able to produce a select number of spark arrester and silencer products for the most popular and late model brands. Of the available aftermarket replacement silencers and combination silencer and spark arresters, few are designed to produce adequate silencing: most are designed to modify engine performance. Thus for a large majority of motocross bikes in existence, no product is commercially available to adequately silence or capture sparks for trail riding purposes.